Odd how air is in only excluded element, but of course this is just up to your personal preference so is not an issue.

For the backpack blocking, it sounds like an automatic one block attack? I assume it hits something hard by sheer luck but breaks it to explain one block? Or the shadows bloc it but why limited to one block? It would make more sense just to leave it open ended where the shadows can block as many attacks as it reasonably could and no auto block.